1. Field of the Invention
The present invention relates to the field of microcontrollers or microprocessors embarked (integrated) with other functions in a same circuit. These other functions typically are memories, specific peripherals or other microprocessors. For example, the design of new circuits more and more often uses reusable microprocessor cores, generally called “virtual components”. This technique enables, for a given application, designing a circuit perfectly adapted to the needs, while taking advantage of an already known and tested microprocessor core. The miniaturization of integrated circuits is thus taken advantage of, not only for associating the microprocessor with other processing circuits linked to the application, but also for miniaturizing the processor itself.
The present invention relates to the protection of the programs and/or data contained in an integrated circuit integrating a microprocessor and one or several memories. More generally, it is desired to control the access to memories of which the signals transiting on physical links (buses) of exchange with the microprocessor are not directly measurable by an electronic device.
2. Discussion of the Related Art
It is indeed desirable to protect the application programs of the integrated circuit as well as some data. For the programs, this protection is intended, in particular, to avoid piracy of the programs designed by a given designer and avoid an incidental disappearing of the programs.
A current solution consists of using fuse-type means to definitively block the access to some memories of the integrated circuit. However, a disadvantage is that these memories are then no longer accessible, even by an authorized designer, in the context of servicing operations.
Another known solution is to give an access code to be provided to the integrated circuit to authorize access to one of its memories. A disadvantage of this solution is that it is enough to know this access code to get round the protection.